Identifying reusable functions in code using specification driven techniques

The work described in this thesis addresses the field of software reuse. Software reuse is widely considered as a way to increase the productivity and improve the quality and reliability of new software systems. Identifying, extracting and reengineering software. components which implement abstractions within existing systems is a promising cost-effective way to create reusable assets. Such a process is referred to as reuse reengineering. A reference paradigm has been defined within the RE(^2) project which decomposes a reuse reengineering process in five sequential phases. In particular, the first phase of the reference paradigm, called Candidature phase, is concerned with the analysis of source code for the identification of software components implementing abstractions and which are therefore candidate to be reused. Different candidature criteria exist for the identification of reuse-candidate software components. They can be classified in structural methods (based on structural properties of the software) and specification driven methods (that search for software components implementing a given specification).In this thesis a new specification driven candidature criterion for the identification and the extraction of code fragments implementing functional abstractions is presented. The method is driven by a formal specification of the function to be isolated (given in terms of a precondition and a post condition) and is based on the theoretical frameworks of program slicing and symbolic execution. Symbolic execution and theorem proving techniques are used to map the specification of the functional abstractions onto a slicing criterion. Once the slicing criterion has been identified the slice is isolated using algorithms based on dependence graphs. The method has been specialised for programs written in the C language. Both symbolic execution and program slicing are performed by exploiting the Combined C Graph (CCG), a fine-grained dependence based program representation that can be used for several software maintenance tasks

Structural testing techniques for the selective revalidation of software

The research in this thesis addresses the subject of regression testing. Emphasis is placed on developing a technique for selective revalidation which can be used during software maintenance to analyse and retest only those parts of the program affected by changes. In response to proposed program modifications, the technique assists the maintenance programmer in assessing the extent of the program alterations, in selecting a representative set of test cases to rerun, and in identifying any test cases in the test suite which are no longer required because of the program changes. The proposed technique involves the application of code analysis techniques and operations research. Code analysis techniques are described which derive information about the structure of a program and are used to determine the impact of any modifications on the existing program code. Methods adopted from operations research are then used to select an optimal set of regression tests and to identify any redundant test cases. These methods enable software, which has been validated using a variety of structural testing techniques, to be retested. The development of a prototype tool suite, which can be used to realise the technique for selective revalidation, is described. In particular, the interface between the prototype and existing regression testing tools is discussed. Moreover, the effectiveness of the technique is demonstrated by means of a case study and the results are compared with traditional regression testing strategies and other selective revalidation techniques described in this thesis

A Transformational Reengineering System That Supports Software Maintenance Using a Graph Representation for the Identification of an Object-Oriented Software Architecture.

The process of maintenance and enhancement of legacy software systems is a laborious and unavoidable task. Often these systems lack structure or modularity, as they were developed using programming languages and paradigms that do not incorporate object-oriented features and sound design principles. The software engineer\u27s task can be simplified if tools are available to identify object like features in the code. These tools can help transform the non-object-oriented code to object oriented code. This research describes a comprehensive and systematic process for transformational reengineering of legacy systems. Research in reengineering is mainly focused on clustering techniques that group procedures present in the legacy system into candidate objects. These clustering approaches are limited to systems with well-defined data structures and procedures. Several of these approaches are either not comprehensive, limited to certain types of systems, or depend extensively on engineer knowledge of the system. Unlike these approaches that analyze legacy systems at the procedural level, the reengineering process we present analyzes systems at the statement level. This process results in the identification of object operations. These operations, along with the state variables and the user defined data structures, are arranged in a hierarchy that represents the object structure of the reengineered variant of the legacy system. From this system hierarchy, objects are identified and encapsulated by streamlining the interfaces. The reengineering process is incorporated in a tool, ReArchitect. Programs are statically analyzed and represented as a statement dependence graph (StDG) for further processing. The StDG is a fine-grained representation with modular representation for functions and program slices. It can adapt to program changes, unlike other representations. The StDG is restructured by merging cohesive components in the graph. The restructured graph is used to build the object structure, which is used to identify the objects. The StDG is a theoretically sound framework that provides support for many problems found in the reengineering domain. We show the value of the StDG in two such domains: program slicing and maintenance. The StDG is restructured differently for different requirements (space/time), and for different types of applications

Design Information Recovery from Legacy System COBOL Source Code: Research on a Reverse Engineering Methodology

Much of the software in the world today was developed from the mid-1960s to the mid- 1970s.This legacy software deteriorates as it is modified to satisfy new organizational requirements. Currently, legacy system maintenance requires more time than new system development. Eventually, legacy systems must be replaced. Identifying their functionality is a critical part of the replacement effort. Recovering functions from source code is difficult because the domain knowledge used to develop the system is not routinely retained. The source code is frequently the only reliable source of functional information. This dissertation describes functional process information recovery from COBOL source code in the military logistics system domain. The methodology was developed as an information processing application. Conceptual and logical models to convert source code to functional design information were created to define the process. A supporting data structure was also developed. The process reverse engineering methodology was manually applied to a test case to demonstrate feasibility, practicality, and usefulness. Metrics for predicting the time required were developed and analyzed based on the results of the test case. The methodology was found to be effective in recovering functional process information from source code. A prototype program information database was developed and implemented to aid in data collection and manipulation; it also supported the process of preparing program structure models. Recommendations for further research include applying the methodology. to a larger test case to validate findings and extending it to include a comparable data reverse engineering procedure